Figure 2. SCD-O cells replicate morphology and ultrastructure of in vivo osteocytes.

TEM imaging of SCD-O osteocytic cells at culture day 15 (a) and osteocytes from murine cortical bone (b) showing the pericellular space (PS), surrounding matrix (M), and dendrite-like processes (P). Confocal images of SCD-O cultures (day 15), outside of mineralized nodules (c, f) or within nodules (d, e, g, h). Cells stained for actin (green) (c–e) or with an Ab to anti-E11 (f–h). Cells in nodules had small cell bodies with discrete actin stress fiber staining localized to cell processes, characteristic of osteocytes (d). Zoomed images highlight numerous cellular extensions on osteocytic cells (e, white arrows). Cells outside nodules show actin distributed throughout the cell with no cellular projections and large cell bodies (c). E11 staining was not observed in cells outside nodules (f) whereas osteocytic cells within nodules had strong E11 localization (g) with signal highly concentrated in osteocyte processes (h, white arrows).